1. Field of the Invention
The present invention is related to a pull tab enabling the manipulation of the slider of a slide fastener, as well as a slide fastener equipped with such a pull tab, and adapted especially for the closure of shoes, clothes, handbags and other items.
2. Discussion of Background and Relevant Information
Pull tabs for slide fasteners are traditionally constituted of a metallic material. In view of the substantial forces exerted often by the user, they must in fact have great endurance to shock and torsion. But such metallic materials (various alloys, stainless steel, etc.) are rigid materials and, therefore, are almost incapable of deformation, torsion or flexion, which promote tearing of the connector bar, or a deformation of the critical portions of the pull tab, especially when the slide fasteners are located in areas that cannot be easily accessed by the user, such as winter sports boots, for example, wherein gripping with gloves is not easy.
On the other hand, if the closure elements are torn off accidentally, the presence of metallic elements can result in injuries to the user.
Attempts to overcome these disadvantages were directed to considering synthetic materials that were presently commercially available and which were determined to be capable of overcoming the disadvantages of the prior state of the art regarding the manufacture of pull tabs for slide fasteners.
U.S. Patent No. 4,949,434 proposed the manufacture of pull tabs enabling manipulation of the slider of a slide fastener, constituted of a synthetic material having properties of elasticity, such as a synthetic elastomer, and especially a polyester elastomer.
The amorphous phase of such copolymers is of the ester or ether type, whereas the rigid phase is of the polybutylene terphthalate type.
This choice of material does have disadvantages, however. In particular, polyester or polyether block ester elastomers are extremely sensitive to ultra-violet radiation. Although their yellowing is limited, their mechanical characteristics decrease sharply with prolonged exposure. As such, they must be provided with anti-UV protection by means of appropriate additives.
On the other hand, they are often difficult to dye and their resistance to wear and tear due to abrasion is not always satisfactory.
Also considered was the use of urethane polyether block copolymers. In these copolymers, the amorphous sequence is constituted by the reaction product of a long chain polyol having an isocyanate, while the rigid sequence results from the action of an isocyanate having a very short glycol chain. This type of copolymer owes its reinforcing characteristic to the hydrogen links located between the polymer chains.
These copolymers have excellent resistance to traction as well as to wear and tear by abrasion, but it must be noted that they become substantially yellow under exposure to ultraviolet rays and also that a large number of such polymer types display a pronounced rigidity at low temperatures.